1. Field of the Invention
This invention relates in general to improvements in cleaning apparatus of the type used, for example, in electrostatic document printers or copiers to remove residual toner, carrier, dust, lint, paper fibers, and the like, from a moving surface, typically in the form of an endless web. More particularly, it relates to a bracket/backup shoe assembly for precisely and repeatedly positioning a customer-replaceable cleaning cartridge adjacent to a moving web that is to be continuously cleaned by such cartridge.
2. Description Relative to the Prior Art
Many electrophotographic printers/copiers use endless webs for recording and/or transferring images, as well as for conveying image-receiving sheets (typically sheets of paper) between image-transfer and other image-processing stations within the instrument. To assure high quality results, it is necessary to maintain the surfaces of such webs free of particulate contaminates (toner, dust lint paper fibers, etc) that may ultimately transfer to the image-receiver sheet or otherwise degrade the quality of images produced thereon. Heretofore, a variety of web-cleaning devices have been devised and used to satisfy this need. One such device is generally referred to as a “blade cleaner” and, as its name suggests, it comprises one or more elongated flexible blades having an edge positioned to contact a moving web to either scrape or wipe particles from the web, depending on the angle of contact between the blade and the web surface. Different types of blade cleaners, both scrapers and wipers, are disclosed, for example, in U.S. Pat. No. 5,426,485 in which cleaning blades serve to remove particulate material from an endless elastic belt used to convey copy sheets in an electrostatic copier.
In U.S. Pat. No. 4,866,483, a blade-type cleaning station is disclosed for use in a table-top electrostatic printer. Here, a pair of spaced, parallel cleaning blades set to operate in a wiping mode, serves to remove or scavenge residual toner from an endless photoconductive image-recording belt following transfer of a toner image to a copy sheet. As the image-recording belt moves along its endless path, scavenged toner falls into a sump from which it is continuously removed by a rotatably driven auger. The rotating auger, which is located in the bottom of the sump, serves to transport the scavenged toner to a remote receptacle that can be readily removed from the machine and emptied by the operator. In this disclosure, the cleaning station is rigidly mounted on the printer's base frame. To gain access to the cleaning station for servicing, and the like, the entire print engine, including the image-recording belt, is mounted on a pivoting frame for movement towards and away from the cleaning station. As it moves towards the cleaning station, the print engine's image-recording belt pressingly engages the respective edges of the cleaning blades and is thereby positioned to be cleaned by the blades as the belt advances along its endless path. Upon being moved away from the cleaning station, sufficient space is eventually provided to enable the machine operator or service personnel to service the cleaning station, e.g., to vacuum scavenged toner from that portion of the sump directly beneath the cleaning blades, or to replace the cleaning blades themselves.
While the cleaning station disclosed in the above-noted patent affords certain advantages not found in prior devices, it may still be viewed as problematic in certain respects. For example, the rotating auger system used to transport scavenged particles from the blade cleaner to a remote receptacle for removal is a relatively complex and costly component of the machine, one that is subject to eventually fail. Further, since the cleaning station is fixed within the machine frame, service access can only be effected by pivoting the relatively heavy print engine through a large arc away from the cleaning station. This, of course, necessitates a relatively formidable and complex mounting mechanism, one that is capable of handling and counter-balancing the relatively heavy weight of the print engine. Ideally, the print engine should remain stationary, and the cleaning station, like most other image-processing stations, should be movable relative to it. Further, once the print engine has been pivoted to its service position to gain access to the scavenged particle sump for vacuuming, blade replacement, etc., the entire sump is exposed to ambient air, and any air currents in the vicinity of the open sump, as occurs during movement of the print engine, can have the effect of blowing toner, dust, etc. throughout the instrument. Ideally, the scavenged particle sump should be easily removed from the vicinity of the machine frame while scavenged particles are confined therein. Once removed, the sump can then be discarded and replaced with a new sump, or it may be cleaned at a location safely spaced from the machine and then replaced. Further, since there is no hard back-up for the web to resist the pressure applied on the web applied by the cleaning blades, the web is likely to stretch over time, thereby changing the dynamics at the blade edge/web interface.
In the cross-referenced patent application noted above, the subject matter of which is incorporated herein by reference, a customer-replaceable web-cleaning cartridge is disclosed that addresses some of the short-comings noted above. In the embodiment disclosed, an endless web to be cleaned is part of a conveyor system used to transport image-receiver sheets past one or more image-transfer stations in an electrophotographic printer. The web-cleaning cartridge comprises a pair of cleaning blades positioned to operate in a wiping mode to scavenge particles from the web surface, and a sump housing that serves both to support the cleaning blades and to collect and retain particles wiped from the web by the blades. Preferably, the cartridge blades are designed to cooperate with a hard backup “shoe” located on the opposite side of the web surface from that contacted by the blades to produce a uniform wiping pressure across the web width while minimizing any tendency for the web to stretch. It is also preferred that the cleaning cartridge be fabricated so as to be disposable after the sump housing has become filled with particles. Thereafter, the cartridge can be readily replaced with a new cartridge. This replaceability of the cartridge necessitates a reliable mechanism by which each new cartridge can be precisely positioned in contact with the web surface with the cleaning blades exerting a predetermined and uniform pressure on the web across its entire width. Further, such a mechanism should enable the cartridge to be easily moved between its operative position and a service position in which the cartridge blades, seals, lid, etc can be removed, serviced and, if necessary, replaced.